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Examination of the effect of tool mass and work postures on perceived exertion for a screw driving task.

The effects of tool mass and work postures on perceived exertion during a screw driving task were investigated. Subjects were nine male and nine female industrial workers, and the task was to drive screws into perforated sheet metal at three vertical (64, 114, and 165 centimeters (cm)) and two horizontal (13 and 63cm) locations using three levels of tool mass (1, 2, and 3 kilograms (kg)). Subjects completed a body part discomfort survey. Results showed that the interaction between tool mass and work location was not significant. However, ratings of perceived exertion increased with each incremental rise in tool mass for all vertical and horizontal work locations. Overall, the right lower and upper arms were reported as uncomfortable for all work locations, and the median ratings increased with each incremental rise in tool mass. The lowest ratings of perceived exertion were at 114cm on the vertical surface, and at 13cm on the horizontal surface. For the horizontal surface, the neck and right arm were identified as uncomfortable at 13cm and 63cm. For the vertical surface, uncomfortable ratings were given for the lower back and right arm at 64cm, the right arm at 114cm, and the right arm and chest at 165cm. The authors conclude that workstation design guidelines based on psychophysical research can reduce the occurrence of work related disorders. Design guidelines were presented for driving screws in industrial work.